MOLYBDENUM PERMALLOY FOR INDUCTANCE COILS 399 



obtain proper separation of the frequency bands of the various chan- 

 nels or to insure suitable transmission properties of the individual 

 channels. While these networks involve coils, condensers and crystals, 

 it is frequently the case that their size, cost and performance are de- 

 termined chiefly by the quality factor Q of the inductance coils. This 

 follows from the fact that Q values of coils are usually considerably 



Fig. 11 — New and superseded cases containing 200 exchange area coils. 



lower than those obtainable readily in condensers and crystals. Ac- 

 cordingly, it is very desirable to have as high a value of Q as possible 

 economically. In addition, such coils must have low hysteresis 

 resistance to limit modulation, and a low temperature coefficient of 

 inductance to secure stability of attenuation or impedance charac- 

 teristics of the filters and networks. 



Due to the improvements in these respects, molybdenum-permalloy 

 core coils can be used quite extensively in new types of carrier tele- 



